It has been well-known that hydrous form and anhydrous form are usually present as forms of crystalline saccharide, and the hydrous crystal can be converted into the anhydrous crystal and vice versa. Trehalose and maltose can be advantageously used in an industrial scale by using those characteristics of converting the forms between hydrous and anhydrous crystal.
Trehalose (α-D-glucosyl α-D-glucoside) is a non-reducing disaccharide where two glucose molecules are bound via α,α-1,1 linkage, and usually obtained as di-hydrate (hereinafter, simply called as “hydrous crystalline trehalose”). While, anhydrous crystalline trehalose can be obtained from the concentrated solution with a moisture content of lower than 10% (w/w). Also, hydrous crystalline trehalose can be converted into anhydrous crystalline trehalose by drying in vacuo at a relatively high temperature. Hydrous crystalline trehalose is stable and hardly adsorbs moisture at the relative humidity of 90% or lower. Anhydrous crystalline trehalose easily absorbs moisture and is converted into stable hydrous crystalline trehalose. By using the characteristic, anhydrous crystalline trehalose can be applied for the powderization of foods containing moisture (Ref. Japanese Patent No. 3,168,550). Hydrous crystalline trehalose is commercialized by Hayashibara Shoji Inc., Okayama, Japan, as “TREHA®”. Also, anhydrous crystalline trehalose is commercialized by Hayashibara Biochemical Laboratories Inc., Okayama, Japan, as a reagent.
Maltose has been called as “malt sugar”, and is a reducing disaccharide where two glucose molecules are bound via α-1,4 linkage. Since maltose has a reducing end, i.e., an aldehyde group, α- and β-anomers are present in maltose. Maltose is usually obtained as crystalline β-maltose mono-hydrate (hereinafter, simply called as “hydrous crystalline β-maltose), produced in an industrial scale and commercialized. While, anhydrous crystalline maltose can be obtained from the concentrated solution with a moisture content of less than 5% (w/w) (Ref. Japanese Patent Kokai No. 43,360/93). Since the anhydrous crystalline maltose contains 55 to 80% (w/w) of α-anomer and 20 to 45% (w/w) of β-anomer, the entity is α/β complex crystal. However, since the anhydrous crystalline maltose has a high α-anomer content, it is usually called as “anhydrous crystalline α-maltose” (Ref. Japanese Patent Kokai Nos. 43,360/93 and 10,341/95). The anhydrous crystalline α-maltose is commercialized by Hayashibara Shoji Inc., Okayama, Japan, as “FINETOSE®”. Japanese Patent Kokai No. 59,697 and J. E. Hodge et al., “Cereal Science Today”, Vol. 17, 7, pp. 180-188 (1972) disclosed anhydrous crystalline β-maltose. However, since the anhydrous crystalline β-maltose has a defect of easily absorbing moisture, it has not been produced in an industrial scale. Since anhydrous crystalline maltose is converted into stable hydrous crystalline β-maltose by absorbing moisture and the resulting hydrous crystalline β-maltose is stable and hardly absorbs moisture at a relative humidity of 90% or lower, anhydrous crystalline α-maltose can be applied for the powderization of foods containing moisture (Ref. Japanese Patent Kokai Nos. 43,360/93 and 10,341/95).
If crystalline saccharide, having different physical properties from those of well-known hydrous or anhydrous crystalline saccharide, can be obtained, it is expected that the field of using crystalline saccharide will be expanded. For example, in the case of sucrose, granulated sugar is known to be produced by shaping sucrose into granule form for improving adhesiveness and solubility and used for frozen dessert such as yoghurt. The granulated sugar has about 10-folds larger specific surface area than crystalline sucrose, but the specific surface area is mere about 0.1 m2/g. Any crystalline saccharide, having more large specific surface area, except for sucrose, is hitherto unknown.